class Student {
    fullName: string;

    constructor(
        public firstName: string,
        public middleInitial: string,
        public lastName: string
    ) {
        this.fullName = firstName + " " + middleInitial + " " + lastName;
    }
}

interface Person {
    firstName: string
    lastName: string
}

function greeter(person: Person) {
    return `Hello, ${person.firstName} ${person.lastName}`
}

let user = new Student("M.", "diao", "mao")
// document.body.textContent = greeter(user)
document.body.textContent = user.fullName